One can cycle the temperature of a Polymerase Chain Reaction (PCR) device for DNA replication in a reacting volume by physically moving the volume through separate heat zones of a microfluidic device by using a channel of suitable length and geometry. Typical PCR systems have fluids in a relatively large chamber and cycle the temperature around the chamber. Other systems use flexible tubing to cycle fluids past heated zones. A problem with conducting PCR in rigid, planar microfluidic devices is that it can be difficult to make a good thermal connection, and thus the results can be inconsistent and unreliable. In order to reduce costs and manufacturing complexity, it is desirable for the thermal management system be an external device that can be attached to the microfluidic assembly. The number of thermal zones on the microfluidic device, the temperature ranges of the thermally active zones, and the zone's proximity to each other all restrict the design choices that can be made concerning a thermal management device. The following invention uses floating thermal contacts to enable PCR reactions. Described, is a device for managing the heating and cooling of multiple areas on an external part or assembly, through the use of isolated, movable, and conductive zones, thereby enabling very efficient PCR reactions. Citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention.